The resonance transducers known from prior art have the disadvantage that the output voltage of the secondary circuit is proportional to the input voltage of the resonance transducer and is predefined to a large extent by the turns ratio of the two coils in the resonance transducer. Further, controlling the circuits described e.g. in [2] is inefficient, because the resonance current flows through all the switching elements which accordingly have to be designed in order to perform in a powerful manner.